Gears are common mechanical devices that are used to transfer rotational forces. A gear is typically a round component with teeth that mesh with other gear teeth allowing the force to be transferred. The gear design, size and orientation are used to transmit the forces at different speeds, torques and direction. Gears are typically used to transfer a mechanical advantage by using gears of different sizes that allow for different rotational gear speeds and torque.
As part of the transfer of forces, the teeth of the one gear engage the teeth of another gear, resulting in gear meshing. For example, when a larger gear engages with a smaller gear, the larger gear rotates at a slower speed than the smaller gear as the teeth of the smaller gear engage a section of the gears of the larger gear.
One type of gear design is helical gear wherein the leading edges of the teeth are angled with respect to the axis of rotation. The gear is curved and the shape of the teeth is a segment of a helix with the angled teeth. The helical gears tend to run more smoothly and generate less noise.
A common application of gears is in relation to a driveshaft that converts engine shaft forces such as used in transmissions and gearboxes. For example, gearboxes of wind turbines typically utilize helical gears to transfer the rotational forces from the rotating shaft of the turbine blades to the engine that generates electrical power.
One of the problems of gear meshing is the precision mating required for efficient, quiet and long-lasting operation of the gear assembly. Factors affecting improper gear meshing include the tolerances of the gears as well as the assembly of the gears within the gearbox housing. These factors can cause noisy operations causing environmental hazards, lower efficiency and increased maintenance issues due to greater wear and tear of the gearbox components. The wear and tear can result in operative losses as well as catastrophic failure of components.
In order to mitigate the above noted problems, certain inspection technologies have been developed, wherein the contact patterns from the gear meshing are evaluated. For example, the teeth of the gears may be coated with a colored paint that shows the wear resulting from the gear meshing. In one example, the gears in the gearbox are painted with a colored coating such as a blue (Prussian blue) or red. During load testing, gears mesh with each other at different loads and different speeds, and due to the contact pressure during meshing the coating wears off on the face of the gears. The wear pattern or contact pattern on the gears at different loads and speeds signifies the quality of the gearbox assembly.
The contact pattern estimation is used to try and determine the acceptability of the gears. In some conventional systems the contact patterns are captured through images using cameras and estimated manually. In such processing, the operator performing the pattern estimation typically has no a priori knowledge of the orientation and distance of the gears. The contact pattern image is selected and manually compared with drawings of an acceptable contact pattern. If the captured images closely match the standards, then the gearbox assembly is accepted. However, there is a lack of quantified methods for accepting/rejecting the gears based on the contact pattern characteristics. The operator driven and manual process of comparison with standard photographs or drawings has limitations such as operator dependence and a qualitative nature of gear pattern quality determination. Improvements to the gear inspection and contact pattern estimation systems and process are desired in the industry.